The invention relates to a method and to a device for incrementally determining the actual reversal of a rotary drive that follows on after a preceding signal switching the rotational direction.
Methods and devices of the above-mentioned type are required e.g. in actuators as information for ascertaining the position of a moving part moved by the actuator. Preferred examples of such moving parts, in practical applications, include motorized window lifters and sunroof drives in motor vehicles, in particular those equipped with a quick-reaction closing power restriction capability. Such a capability is provided in motor vehicles to prevent persons"" arms and such from being pinned by the moving part and are therefore subjected to increasingly rigorous safety standards.
In order to determine the respective opening or closing position and direction of rotation of a motor vehicle closing part driven by a rotary drive, the device ordinarily includes an incremental transmitter system having a rotary-side transmitter wheel and a sensor on the stator-side that detects the signals of the rotating transmitter wheel. Such a device is known, e.g., from German Laid-Open Publication DE 42 33 549 A1, which discloses fashioning the rotary-side transmitter wheel of the incremental transmitter system as an asymmetrical magnet wheel e.g. on the drive of an armature of the electrical motor driven by the actuator. The sensor on the stator side is preferably a Hall sensor detecting the signals of the rotating transmitter wheel. Changes in cogs or polarity cause the rotating transmitter wheel to generate (if necessary after some signal processing) a basically rectangular pulse signal having flanks defined by high and low signals, respectively. This rectangular pulse signal can also be coded for determining the rotation direction of the transmitter wheel.
When the device detects a restriction of movement of the closing part, the motor of the actuator causes the closing part to reverse direction by changing the polarity of the supply voltage of the actuator, for instance in the manner disclosed in German Laid-Open Publication DE 43 16 898 C2. Due to electrically inductive and/or mechanical inertia, the actual mechanical reversal in direction of rotation takes place with a certain time lag in relation to the switch in the signal itself which causes the change in direction of rotation by changing the polarity of the supply voltage. The timing and the position of the actual rotation reversal is therefore not identical to the timing of the voltage reversal. If no second stator-side sensor is provided and circumferentially offset in relation to the first stator-side sensor, the timing and position of the actual rotation reversal cannot be determined from a phase comparison of the detected flank signals of the two sensors.
According to one object of the present invention, the actual mechanical reversal of the rotation direction of a rotary drive, following a switching signal electrically switching the rotation direction should be detectable and assignable to the corresponding correct pulse signal value count of the respective position of the moving part being moved by the rotary drive. The determination of the actual reversal of the rotary drive allows the pulse signal value count to be properly correlated with a pulse count value reference template defining the entire range of motion of the moving part, e.g. from a fully open position to a fully closed position. This, in turn, ensures that reversals of the rotation direction do not give rise to errors in the correlation, which could otherwise, e.g., lead to undesirable differences between, e.g., the calculated fully closed position and the actual fully closed position of the moving part. A further object of the invention is to reduce the design and production costs for devices that determine the actual reversal of the rotary drive. In particular, it is an object to provide such a device that utilizes only a single stator-side sensor.
According to one formulation of the invention, these and other objects are solved by a method for incremental determination of an actual reversal of a rotary drive that follows on after a preceding signaled switch in rotary direction, which includes: (i) defining the rotation of the rotary drive with a sequence of pulse signals that are proportional to the rotational speed of the rotary drive, with an intermittent reference signal that differs from the pulse signals; (ii) counting the pulse signals on a stator side; and (iii) determining the actual reversal of the rotary drive after the signaled switch in rotational direction by utilizing a pulse signal correction value, and by utilizing a change from a monotonous increase to a monotonous decrease of pulse signal lengths of the pulse signals. The pulse signal correction value is derived from counting the pulse signals between respective occurrences of the reference signal before and after the actual reversal of the rotary drive.
According to another formulation of the invention, there is provided a device for determining an actual reversal of a rotary drive that follows on after a preceding signaled switch in rotary direction, which includes: (i) an asymmetrical rotor-side transmitter producing a sequence of pulse signals that are proportional to the rotational speed of the rotary drive, and an intermittent reference signal that differs from the pulse signals; (ii) one single stator-side sensor receiving the signals from the rotor-side transmitter wheel and outputting a stator-side signal count value; and (iii) an evaluating device forming a pulse signal correction value derived from a count of the signals between respective occurrences of the reference signal before and after the actual reversal of the rotary drive and adjusting the stator-side signal count value, based on the pulse signal correction value, to reflect the actual reversal of the rotary drive.
On the basis of the method in accordance with the present invention, the number of poles, or the number of pulse signals, between two reference signals rotating past the single stator-side sensor, one after the other, is counted. Herein, the first reference signal is associated with the initial rotation direction and the following reference signal is associated with the subsequent, opposite direction of rotation, since the actual reversal in the direction of rotation of the rotary drive lies intermediate between the two reference signals. In order to obtain the correct actual total pulse signal pulse count value, it is necessary to subtract the number of pulse signals counted within this time frame from the otherwise incorrect total pulse signal count value. This incorrect total pulse signal count value requires adjustment, in particular, because it includes additional pulse signals generated, due to induction, through the second reference signal. However, by subtracting the above-noted pulse signal correction value, one obtains the correct actual added-together total pulse signal count value corresponding to the actual current position of the moving part moved by the rotary drive. As noted above, the moving part is preferably a motor vehicle window or a motor vehicle sunroof.